Revealing mistake: In the scene of the 20th game (the following shot after Brad Pitt leaves the field) we see Jonah Hill looking at him. An extra to the left pulls out his smartphone (which in 2002 was years away from release) and proceeds to take a picture of Jonah Hill.
Moneyball (2011)
1 revealing mistake - chronological order
Directed by: Bennett Miller
Starring: Brad Pitt, Philip Seymour Hoffman, Jonah Hill, Robin Wright, Stephen Bishop
Genres: Drama
Other mistake: Shortly after Billy Beane arrives for the 20th consecutive win game, Raul Ibanez is announced as the batter despite being on second base at the time.
Billy Beane: You think losing is fun?
Trivia: Although it isn't shown in the film, Billy Beane managed, by using Paul DePodesto's sabermetric analysis, to get thirteen of the twenty players he wanted in the 2002 amateur draft. At the time, this was unprecedented; no GM before had ever finished the draft with more than six of their top choices, and most GMs are lucky to even get their top two or three choices.